Study of the effects of the operating conditions of a decanter centrifuge on a pilot-scale protein recovery setup from cold-pressed rapeseed press cake

Sammanfattning: There is significant evidence to suggest that diets that include high levels of meat consumption have negative effects on both the environment and human health. As a result, efforts are being made to identify and characterize more plant-based proteins, such as those found in rapeseed. Rapeseed is the second-largest oilseed crop worldwide and is primarily used to produce edible oils through mechanical separation methods. During this process, a protein-rich by-product called press cake is produced, which is currently utilized as a source of protein in animal feed. Rapeseed press cake primarily consists of fibre (30%), protein (27-30%) and residual oil (20%). The use of rapeseed protein in food is limited because of its bitter taste and the antinutritional components it contains. In order to effectively recover protein from rapeseed press cake, it is necessary to scale up the process beyond laboratory-scale setups. Researchers from the Department of Food Technology, Engineering and Nutrition at Lund University have successfully achieved this; consequently, the current study aimed to further enhance the process's capacity and protein recovery yield in a pilot-scale setup. The study aimed to recover proteins from rapeseed press cake using the salt extraction method at a concentration of 0.25M and a pH of 7, followed by isoelectric precipitation at pH 3.5 and a decanter centrifuge. The optimal processing parameters for the decanter centrifuge during the first protein recovery step were an inlet feed rate of 60 L/h, 2000xg acceleration, 50 rpm differential speed, and a weir disc with an inner diameter of 68 mm. A pH of 7 was suitable for a gentler extraction of proteins, with the addition of sodium chloride resulting in an extraction coefficient of 61%. Based on thorough analysis, it was determined that the most suitable set of processing parameters for the second phase of protein recovery were an inlet flow rate of 10 L/h, 4000xg acceleration, 6 rpm differential speed, and a 56 weir disc inner diameter. The latter enhanced the overall process capability without any adverse effects on critical factors such as dry matter and protein content of the precipitate. The study found that scraping equipment surfaces resulted in a significant increase in protein recovery yield. The yield increased from 17% to 29% under the selected processing conditions.